﻿// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System.Diagnostics;
using System.Runtime.CompilerServices;

namespace System.Buffers
{
  internal static class Utilities
  {
    //[MethodImpl(MethodImplOptions.AggressiveInlining)]
    internal static int SelectBucketIndex(int bufferSize)
    {
      Debug.Assert(bufferSize > 0);

      uint bitsRemaining = ((uint)bufferSize - 1) >> 4;

      int poolIndex = 0;
      if (bitsRemaining > 0xFFFF) { bitsRemaining >>= 16; poolIndex = 16; }
      if (bitsRemaining > 0xFF) { bitsRemaining >>= 8; poolIndex += 8; }
      if (bitsRemaining > 0xF) { bitsRemaining >>= 4; poolIndex += 4; }
      if (bitsRemaining > 0x3) { bitsRemaining >>= 2; poolIndex += 2; }
      if (bitsRemaining > 0x1) { bitsRemaining >>= 1; poolIndex += 1; }

      return poolIndex + (int)bitsRemaining;
    }

    //[MethodImpl(MethodImplOptions.AggressiveInlining)]
    internal static int GetMaxSizeForBucket(int binIndex)
    {
      int maxSize = 16 << binIndex;
      Debug.Assert(maxSize >= 0);
      return maxSize;
    }
  }
}
